This invention relates to an electrode assembly which is implantable in a human or animal body around a nerve. Typically, the electrode is connected by a wire or wires to an implanted electronic biostimulator which can be remotely programed, or by an electronic circuit commanded by an external wireless telemetry transmitter to deliver electrical signals to the nerve. The thus stimulated nerve in turn causes a reaction in one or more muscles to achieve a desired result, such as bladder control for a patient who has lost normal control due to injury or disease.
My U.S. Pat. No. 4,573,481 (the disclosure of which is incorporated herein by reference) describes in greater detail the various types of nerve-stimulating electrodes (e.g. cuff electrodes) which have been used in the past, and the problems which have been encountered with installation and use of these prior-art units. For brevity, the reader is referred to this patent for further background information.
The aforementioned patent discloses a spiral or helical electrode which solves many of the shortcomings of earlier designs, and is wound around the nerve of interest during surgical installation. Excellent results have been obtained with this electrode, but there are occasions where space around the nerve is limited, and the manipulation of the helix to wind it around the nerve demands skillful and painstaking care by the surgeon.
The electrode assembly (and associated installation tool) of the present invention incorporates the important advantages of my earlier helical design, and provides significant placement simplification and reduction of trauma risk during installation. Broadly, the new assembly is a flexible electrode-supporting matrix forming two oppositely directed helical portions extending from a central bridge or junction. Each helical portion extends circumferentially somewhat more than 360 degrees (typically about 420 to 540 degrees).
During installation, a tweezer-like tool has a pair of pins or tines which are fitted into the open central bore of the helical matrix. The tines are then expanded to distort and open the flexible helices so a laterally open passage is formed along the length of the matrix. The electrode assembly is then fitted over the nerve in a direction generally perpendicular to the length of the nerve. The tines are withdrawn to enable the matrix to close gently around the nerve to place one or more conductive electrodes in intimate contact with the nerve surface. Contrarotation of the several spiral or helical matrix portions provides a further advantage of improved electrode-assembly anchorage and resistance to unwanted movement along the nerve in response to movement of adjacent tissue or skeletal structure.